There are two main past tenses :
The imperfect (je mangeais) translates to the English imperfect (I was eating).
The passé composé (j'ai mangé) translates to the English present perfect (I have eaten) but can also be translated as the English simple past (I ate) or the emphatic past (I did eat).
Basically, we use Imparfait to describe past ongoing situations ("J'allais en France" means "I was going to France") and passé composé to express one or more events or actions that began and ended in the past. ("Je suis allé en France" means "I went to France").